It is known in the prior art to integrate a protective capacitor to act as a high-pass filter within an antenna. Such a protective element allows the radio frequency function of a whip antenna while providing substantial series impedance in the event of unintended contact with over-head high-voltage electric lines that a vehicle employing a large whip antenna may encounter. For example, the patents to Pokryvailo et al., U.S. Pat. No. 6,366,251, and Goodall et al., U.S. Pat. No. 4,513,338 describe methods of high voltage protection, but they do not integrate an unintended electric charge dissipation methodology. Ironically, both of the above patents disclose an antenna that can create a condition of a dangerous static charge build up that can result in harmful electric shock if a human body acts as a discharge path for the accumulated charge. Radio equipment may be damaged by this unintended accumulated electric discharge event. When such discharge paths are created temporarily around the whip antenna's base insulator, the fast rise-time of the discharge pulse consists of theoretically infinite and intense radio frequency spectral components that are capable of damaging sensitive radio communication equipment.
Accumulated electric charge may result from natural phenomena such as rain static and more recently observed, desert air plasma effects. A desert air plasma effect is a condition where a vehicle employing a whip antenna accumulates an electric charge resulting from a “far-off” lightning storm system while placed in a desert environment. It is speculated that a plasma field condition originating from the storm cloud system, propagates electric plasma through the dry desert air that results in a substantial charge build-up in the antenna system that is employing a “high-voltage protection device/capacitor.” This charge build-up continues until a resulting uncontrolled electric discharge event manifests itself. This charge effect has resulted in “gun shot” like sounding discharge events that can be very disconcerting in a desert military theater of operations as well as causing damage to communications equipments.
The patent to Pokryvailo et al., U.S. Pat. No. 6,366,251, discusses a “non-linear capacitor” that is characterized by a negative low-frequency voltage coefficient, whereby the passage of a high frequency alternating current remains essentially unaffected. This patent discloses that the inventors, after having tested numerous off-the-shelf capacitors, lay claim to some desirable attributes of a particular inherent flaw in some capacitors if not all. They assert that after subjecting a high-voltage rated capacitor, particularly ones that use a strontium-based ceramic, to 24 KV that the value of capacitance decreases. It is further asserted that this has the beneficial effect of increasing the low frequency impedance thereby insuring the current is below 5 milliamperes while continuing to provide minimal effect on the high frequency operation of the whip antenna. It is concluded that the bigger this characteristic drop in capacitance the better and further that this drop is “non-linear.”
It is acknowledged that subjecting any high voltage rated capacitor to 24 KV will cause it to heat up due to inherent losses. The more it heats up, the more it expands, and the more the “plates” move apart and so drops the capacitance. The '251 patent asserts that Goodall et al, U.S. Pat. No. 4,513,338, is flawed because a capacitor using a Teflon™ dielectric is “linear” and therefore cannot possibly be designed to limit low frequency current to below 5 milliamperes while passing an “unobstructed” high frequency current. Goodall teaches that a value of “linear” capacitance, typically 500 picofarads, can be achieved that will limit low frequency current to below 5 milliamperes with an attendant whip antenna that can be designed to correctly function in its presence. The “unobstructed” high frequency current may be a matter of subjection, since if the value of capacitance has indeed deceased, the capacitive reactance (the obstruction) has increased by the well known relation: Xc=1/(2*π*f*C). Also, since the capacitance has decreased, one may point out that the high frequency capacitance reactance of the non-linear capacitor may “interfere” more with high frequency whip antenna operations than the linear capacitor once heated up by a high voltage contact event. Without commenting upon the assertions made in the prior art, it is believed that the “hot” capacitance value is lower than the “cold” capacitance value. The bad thing is that the Xc value is also greater at the radio frequency operation of the whip antenna, and could impede its normal operation until “cooled” off.
Therefore, there is a need for a high voltage protection device that prevents accidental electric shock to nearby personnel caused by incidental contact with high voltage electric power lines. And there is a need for the device to also integrate an incidental electric charge bleeder system for the purpose of discharging any accumulated electric charge.